Embodiments of the present invention relate to a method of cleaning and refurbishing process chamber components.
A substrate processing chamber may be used to process a substrate in an energized process gas, such as a plasma, to manufacture electronic circuits, such as integrated circuit chips and displays. Typically, the process chamber comprises an enclosure wall that encloses a process zone into which a process gas is introduced, a gas energizer to energize the process gas, and an exhaust system to exhaust and control the pressure of the process gas in the chamber. The process chamber may, for example, be used to deposit material on a substrate or to etch material from a substrate. For example, the chamber may be used to sputter deposit a material onto the substrate, such as a metal for example, aluminum, copper or tantalum; or a metal compound such as tantalum nitride or titanium nitride.
The chamber components that are exposed in the chamber, such as the surfaces of a chamber sidewall, ceiling, liner, or deposition ring, are often coated with a coating layer that, for example, may serve to enhance the adhesion of sputtered material onto the coating, to increase the erosion resistant of the underlying material to the plasma in the chamber, or to provide some other desirable property, such as have an electrically conducting surface. For example, a chamber component may be made from aluminum oxide or quartz and plasma spray coated with a coating of aluminum. In another example, a component made from a metal can be coated with a ceramic coating, such as an aluminum oxide coating.
These coated components often require frequent cleaning and refurbishing to retain their designed characteristics. For example, when such chamber components are used in PVD processes to sputter deposit material onto a substrate from a target, the sputtered material also accumulates on the surfaces of the component. The accumulated process deposits can cause thermal expansion stresses that result in delamination, cracking, and flaking-off of the underlying coating from the underlying structure. The plasma in the chamber can penetrate through damaged areas of the coating to erode the exposed surfaces of the underlying structure, eventually leading to failure of the component. A refurbishing process is typically performed to clean and refurbish the coated component after a number of substrates have been processed. The refurbishment process may involve removing process deposits, such as sputtered material, that has accumulated on the coating surface, and may also involve re-coating the component with a fresh coating layer. The refurbishment process reduces the incidence of spalling or peeling of the coating from the component during the processing of substrates, and thus reduces the contamination of substrates processed in the chamber.
In one conventional refurbishing process, a “lift-off” process is used to remove the coating from a coated component and to clean the surface of the component. In a typical “lift-off” process, process deposits are at least partially removed by removing the coating from underneath the process deposits, similar to the methods described in “The Science and Engineering of Microelectronic Fabrication”, by Stephen A. Campbell, Oxford University Press, 1996, pages 274-275; and “Silicon Processing for the VLSI Era, Volume 1: Process Technology,” by Stanley Wolf and Richard N. Tauber, Lattice Press, 1986, pages 535-537; both of which are incorporated herein by reference in their entirety.
In one type of conventional lift-off refurbishing process, a coated component having process deposits thereon is first immersed in a basic solution, such as KOH, which strips or dissolves the coating and thereby removes the overlying process deposits, leaving a bare, un-coated component. Following this step, the surface of the bare surface of the component is further cleaned by immersing the surface in an acidic solution, such as a solution of HF and HNO3, to remove the remaining process deposits. The coating can be subsequently re-applied to the component cleaned in the lift-off process. However, the above-described process can cause the refurbished component to have an undesirably low part life, due at least in part, to the corrosive action of the acidic HF or HNO3 solution on the bare surface of the component after the coating has been removed. The acidic solution chemically attacks the bare surface of the component and damages the surface. A coating subsequently applied to the damaged component surface adheres poorly and can peel or flake off from the component surface.
Furthermore, the conventional lift-off process also fails to remove the intermetallic layer which can develop at the interface between the coating and an underlying metal component and which is believed to result from thermal cycling of the parts in the process chamber. This intermetallic layer can weaken the bonding interface between the coating and underlying component, and a build-up of this intermetallic layer can reduce the component part life.
Thus, it is desirable to have a process that is capable of refurbishing and cleaning a component to provide a component having desirable surface properties in a substrate processing environment. It is further desirable to have a method of refurbishing and cleaning a component to provide a component having a good lifetime in fabrication processes in which large amounts of sputtered material may deposit on the component.